Circuit interrupter



Aug. 21, 1962 R. M. KORTE ETAI. 3,050,602

CIRCUIT INTERRUPTER Filed March 7, 1960 2 Sheets-Sheet 1 INVENTORS: Emma/e0 M. Koxrz, HA ROLD M SCHNEIDER 7 A TTORNEY 1962 R. M. KORTE ETAL 3,050,602

CIRCUIT INTERRUPTER Filed March '7, 1960 2 Sheets-Sheet 2 x A SPIRAL WOUND POLE PIECE 3 WITH ROUND CORE FLUX P-DISTANCE B-B l I I 42 FLAT LAMINATED POLE PIECE WITH ROUND CORE VERTEX REGION IN ARC CHUTE WHERE INTERRUPTION TAKES PLACE SPIRAL WOUND POLE PIECE ,8 I6

Fig.6

PHAszMs OFFLUX INARC cwurs N 2 4 a a /o /2 DISTANCE FROM ARC RUNNER REVERSE LOOP 6 FLAT LAMINATED POLE PIECE INVENTORS: F'l' 7 RICHARD M. K0215,

' ARC -vv- HAROLD N. SCHNEIDER A TTORNEY Patented Aug. 21, 1962 hoe 3,050,602 CIRCUIT INTERRUITER Richard M. Korte, Media, and Harold N. Schneider,

Springfield, Pa, assignors to General Electric Company, a corporation of New York Filed Mar. 7, 1960, Ser. No. 13,127 4 Claims. (Cl. 200--147) This invention relates to circuit interrupters and more particularly to are extinguishing structure therefor, and it has for an object the provision of a simple, reliable, improved and inexpensive device of this character.

Another general object of this invention is the provision of an improved circuit interrupter of the air-break type in which the structure of certain parts is such as to produce improved interrupting ability.

In the interruption of an arc with an arc chute type breaker and a propelling magnetic field, proper flux distribution magnitude, and phase lag effectively promote the best performance of the chute. Conventionally, the propelling magnetic flux has been produced by magnetic blow out structures having pole shoes arranged in pairs on opposite sides of the arc chute with an interconnecting yoke or core upon which is mounted a magnetic blow out coil in which the arc current flows. Heretofore two basic types of magnetic blow out structures have been employed to produce the propelling magnetic flux. One of these comprises pole shoes of stacked flat laminations of magnetic material with an interconnecting core of stacked laminations having a rectangular cross section and having an oblong shaped coil mounted thereon. The other comprises solid plate pole pieces with an interconnecting yoke having a round cross section and having a round coil mounted thereon. The oblong shaped coil must be made of a conductor having a larger cross section than that of the conductor of a round coil in order to enable it to withstand the mechanical forces which tend to make it round. For the same number of turns the oblong coil requires a greater amount of copper and consequently, a larger space. If the stacked laminated core were made round, the core laminations could not be interleaved with the pole shoe laminations or joined to them in any other conventional manner and furthermore the junction of a round core with a stacked lamination pole shoe would result in an uneven distribution of the flux crossing the air gap in the arc chute between opposing pole faces. However, it is desirable to use both laminated pole pieces and cores and at the same time to use the mechanically etficient round coil and core. Accordingly, a further object of this invention is the provision of a laminated pole shoe structure with which a core of round cross section can be joined to provide an efiicient magnetic junction and to produce a uniform distribution of propelling flux in the arc chute.

It is desirable to have a relatively small phase lag between the arc current and the arc propelling magnetic flux for the purpose of producing substantial interaction forces between the propelling flux and the magnetic flux surrounding the arc immediately prior to current zero when both flux and the current are relatively small. The use of shading coils to produce phase displacement of flux in a magnetic circuit is well known. However, the use of shading coils in connection with the pole pieces of magnetic blow out structures has certain disadvantages among which are that the phase of all of the flux linked by the shading coil is phase displaced and the use of shading coils adds to the material and assembly cost of the blow out structure. Accordingly, a further object of this invention is the provision of a laminated pole piece structure which inherently produces the desired phase lag of the magnetic flux without the addition of shading coils or any other structural components.

In carrying the invention into eifect in one form thereof the magnetic blow out structure for an arc chute having a pair of spaced apart insulating sidewalls and are runners comprises a pair of magnetic pole shoes arranged in spaced apart relationship with opposite pole faces facing each other and interconnected by means of a yoke member. Each of the pole shoes is formed of substantially continuous strip insulated magnetic ribbon material flat wound into a flat spiral coil of generally oblong shape with each layer in mechanical contact with the next adjacent layer. The yoke member is also formed of continuous strip insulated magnetic ribbon material fiat wound into a flat spiral coil having a round cross section.

For a better and more complete understanding of the invention reference should now be had to the following specification and to the accompanying drawings of which:

FIG. 1 is a side elevational view partly in section showing an electric circuit breaker provided with magnetic blow out structures embodying the invention;

FIG. 2 is a cross sectional view taken along the line 22 of FIG. 1;

FIG. 3 is an end view of the arc extinguishing structure of FIG. 1;

FIG. 4 is a view in perspective of a magnetic blow out are extinguishing structure embodying the invention;

FIGS. '5, 6 and 7 are diagrammatic sketches which facilitate an understanding of the invention; and

FIG. 8 is a chart of characteristic curves which facilitates an understanding of the invention and illustrates its advantages.

Referring now to FIG. 1 of the drawing, the circuit breaker shown therein comprises a pair of terminal bushings 1 and 2, both of which are fixed in position relative to the supporting frame of the circuit breaker. The bushing 2 comprises a downwardly extending conductive stud 3 at the lower end of which a movable conductive switch blade 4 is mounted by means of a fixed pivot 5. At its outer end, the blade 4 carries suitable circuit controlling contacts such as a main current carrying contact 6 and an arcing contact 7.

Bushing 1 comprises a conductive stud 1a to which a downwardly extending conductive member 8 is electrically connected. Attached to this conductive member 8 is a curved contact retaining member 9 which coacts with the member '8 to form a holding pocket for receiving the anchored ends of main stationary current carrying contact fingers 10. These fingers are pivotally mounted on a curved portion 12 of the conducting member 8 and are biased for limited rotative wiping movement in a closing direction by means of suitable compression springs a. These compression springs provide for high pressure circuit closing engagement between the stationary current carrying contact 10 and the movable main current carrying contact 6.

The movable arcing contact 7' cooperates with stationary arcing contact 13, which is mechanically and electrically connected to the conducting member 8 by suitable clamping means 14. The material of which the arcing contacts 7 and 13 are made is capable of withstanding arcing and is also of relatively high resistivity in comparison to the material of the current carrying contacts 10 and 6. Accordingly, when the switch blade 4 is in its closed position as shown in FIG. 1 most of the circuit current flows through the current carrying contacts. It is only when the switch blade 4 is driven counterclockwise to open the breaker that the arcing contacts carry appreciable current. During contact opening action, the current carrying contacts part first, thereby I diverting current through the arcing contacts which are still in engagement owing to their extensive wipe. Thereafter, the arcing contacts part and draw a circuit interrupting arc which is driven into an arc chute and there lengthened, cooled and extinguished.

For driving the switch blade 4 counterclockwise to effect circuit interruption, a reciprocable operating rod 16 pivotally joined to the switch blade at point 17 is provided. When this operating rod is driven upwardly, it acts to move the switch blade counterclockwise to effect a circuit interrupting operation. The circuit can be reestablished by driving the operating rod downwardly to return the switch blade 4 in a clockwise direction to the closed position illustrated in FIG. 1. The operating rod 16, which is made of insulating material, is actuated by means of a suitable conventional operating mechanism (not shown).

The are chute 15 comprises a pair of side walls l8 and :19 constructed of appropriate arc resistant and tracking resistant insulating material. As shown in P18. 3, these side walls are clamped together in spaced apart relationship by means of insulating clamping strips lit and 21. Each side wall is provided with plurality of fins 22 projecting toward the other side wall and arranged to interleave with the corresponding projecting fins on the other side wall, thereby forming a sinuous or Zigzag passage as viewed either from the entrance end r from the exhaust end of the chute. The view from the latter end is illustrated in FIG. 3. As shown in FIG. 2 the edges of these interleaved fins taper toward the entrance of the chute (at the right in FIG. 1) and thereby provide a throat portion through which the arc is first passed before entering the Zigzag passage between the fins 22. These tapering edges have a curvilinear contour and form an angle a known as the arc entrance angle. Each adjoining pair of fins has such an entrance angle and their vertexes all lie on the curvilinear line 23 which constitutes their locus.

For facilitating movement of the are into the arc chute, a pair of conductive arc runners 24 and 25 are provided along opposite edges of the entrance portion of the chute. As shown in FIG. 1, there runners 24 and 25 extend generally transversely to the path of the arc and in a other generally divergent relationship with respect to each other from the region in which the arc is initiated near the arcing contacts.

Associated with the arc chute structure are a plurality of blow out magnets 26, 27 and 23 mounted on the upper arc runner 24 and a similar plurality of blow out magnets 29, 30 and 31 mounted on the lower arc runner 25'. Each of these blow out magnets is a generally U-shaped structure as shown in FIG. 4 comprising a pair of pole shoes 32 and 33 constituting the legs of the U and an interconnecting yoke member *34. Each is mounted on one of the arc runners with its pole plates straddling the arc chute and extending generally in the direction of movement of the arc to a point beyond the locus line 23 of the vertexes of the individual entrance angles. For example, as shown in FIGS. 1 and 3 the pole shoes 32 and 33 of the blow out magnet 28 straddle the clamped side wall members 18 and 19 of the arc chute. Mounted on the yoke members of the blow out magnets are blow out coils 26a, 27a, 28a, 29a, Stla and 31a. As shown, these blow out coils are round and their inside diameters are such that they snugly surround an insulating sleeve member on the round cross section yoke members on which they are mounted. Usually the blow out coils in the upper group are connected in series relationship with each other and th se in the lower group are also connected in series relationship as shown, although other connections are sometimes used for special purposes.

Normally, i.e. when the current carrying contacts 6 and 10 and the arcing contacts 7 and 13 are closed, the blow out coils are not in circuit and are consequently deenergized. The main purpose of these blow out magnets is to propel and to accelerate the movement of the i. are along the runners into the interior of the arc chute and then to produce a pressure gradient to expel the ionized gases. When a particular blow out coil is energized its pole shoes produce a magnetic field transverse to the arc path. This magnetic field reacts with the magnetic field surrounding the arc to produce a resultant force that drives the are at high speed toward the interior of the chute.

The pole shoes are made or": continuous ribbon dynamo silicon steel material that is coated with a suitable insulating varnish and wound to form a tight flat coil. It is not essential that the spiral coil be formed of a single ribbon. It may be formed of a plurality of ribbons wound into the same spiral configuration with the fiat surfaces of adjacent ribbons in contact with each other. For a breaker having a rating in the range of 75 to 1000 mva. the pole shoes would appropriately be wound of ribbon fifteen to twenty-five mils thick and one-fourth to threefourths inch wide. in fabrication, magnetic steel ribbon is wound on a mandrel under suflicient tension to produce a tightly wound spiral coil of circular configuration. When a predetermined number of layers have been wound on the mandrel, the winding operation is stopped and the coil is placed in a press which applies suiiicient force along one diameter to compress it from a circular configuration to the general oblong with semicircular ends configuration illustrated in FIGS. 1 and 4. While still in the press a transverse hole 35 is drilled in the coil at a point near one of the semicircular ends and in from the edge an amount approximately equal to the radius of the circular yoke member 3d To prevent the coil from springing back into its original circular shape when the compression force of the press is released it is tightly wrapped with a plurality of bands 36 of a strong tough tape such for example as a glass filament type tape. However, any suitable type of tape may be used. Each band comprises a sufficient number of wraps to constitute a strong durable binding. Upon completion of the taping operation, the pole piece is removed from the press and preheated and dipped into a suitable insulating compound such for example as plasticized polyvinyl chloride. The bath may be at a suitable temperature such for example as room temperature and the pole shoe is immersed in it for a brief interval, eg. five to ten seconds. After dipping, the pole piece is placed in an oven and kept at a temperature of from to degrees C. for fifteen to twenty minutes to fuse the coating. When this is completed a circular area of the coating surrounding hole 35 having a diameter equal to the diameter of the round yoke member is removed by machining.

The interconnecting yoke or core member 34 is also a spiral coil of ribbon magnetic material having a width equal to the predetermined distance between two pole shoes. The ribbon is wound upon a mandrel into a tight spiral coil having a round cross section. After the winding operation is completed, the coil is tightly clamped and then inserted. into a strong rigid insulating tube. The clamps are then removed and the tendency of the coil to unwind when freed from restraint, causes it to expand and thus to provide a firm tight contact against the inside wall of the tube. A round coil 37 of a good conducting material such as copper is then slipped on the core 34. This coil is the same as any of the coils 26a to 31a inclusive in FIG. 1. it is made preferably by edge winding a strip of insulated conducting material such as copper. The core and coil mounted thereon together with a pair of pole shoes are then assembled into a complete blow out magnet unit by means of a through bolt extending through the holes 35 in the shoes and the axial mandrel opening in the yoke member.

When the switch 4 is driven counterclockwise to open the breaker, an arc is established at the arcing contacts 7 and 13 as soon as these contacts part. After its formation at the arcing contacts, the upper terminal of the are quickly transfers to the upper arc runner 24 thereby con- (B ilecting' the blow out coil 26a in series with the arc. In the meantime the movable arcing contact 4 swings rapidly away from the stationary contact and as it moves into proximity to the lower arc runner, the lower terminal of the arc transfers to the lower arc runner thereby connecting blow out coil 29:: in series with the arc. The energized coil 26a. of blow out magnet 26 immediately produces a magnetic field between the pole shoes 32 and 33 of this blow out magnet transverse to the arc, and the coil 29a produces a similar transverse magnetic field between the pole plates 32 and 33 of blow out magnet 29. As a result of the interaction of these transverse magnetic fields and the magnetic field surrounding the arc itself, the arc is moved rapidly outward on the arc runners 24 and 25. As it moves along the arc runners, it successively inserts the coils of the upper and lower groups of blow out magnets in series with the are thereby progressively to increase the magnetic force tending to drive the arc outward into the arc chute.

As the arc app-roaches the vertex of the entrance angle formed by the interleaving fins it begins heating and vaporizing the chute material from the side walls of the chute and exposed surfaces of the fins with which it is in close proximity. This vaporized chute material, being of substantially lower temperature than that of the plasma, cools it.

As a result of the cooling process, the actual interruption of the arc takes place in the region of the vertexes of the entrance angles between the interleaving fins of the arc chute. That is to say, the interruption takes place in the region of the locus of these vertexes which is represented by the line 23 of FIG. 1. In this region a small amount of phase lag of the propelling flux in the arc chute with respect to the arc current is beneficial because with such a phase lag, the flux will have a substantial magnitude just prior to current zero when the arc current is weak and will maintain the arc in movement into the arc chute toward or beyond the vertexes of the entrance angle where it is interrupted.

We have discovered that for a typical breaker having a rating in the range previously mentioned, blow out magnets provided with spiral wound laminated pole pieces as herein described produce in the region of the vertexes a small, e.g. 8 to 10 degrees phase lag of the flux with respect to the arc current. The spiral wound core is not completely eifective in eliminating eddy currents and the remanent eddy currents which are not eliminated produce the aforementioned phase lag of the flux. Consequently, additional devices such as shading coils are not required to produce the desired amount of beneficial phase lag. The invention has the further advantage of producing substantially less phase lag of the flux in the region of the arc runners than of the flux in the region of the vertexes. Although a certain amount of phase lag in the region of the vertexes is beneficial, phase lag of the flux in the region of the arc runners 24 and 25 is detrimental to best performance. An appreciable phase angle lag of the propelling flux results in reversing the direction of the force acting on the arc in the interval between current zero and the reversal of the propelling flux. In the case of an are that has just transferred to the arc runners immediately prior to current zero, this reverse force following current zero tends to drive the are back toward the arcing contacts and thus to cause a failure. Thus, in the region of the vertexes, e.g. at point x a phase lage of approximately 8 to 10 degrees of the flux produced by the pole shoes of magnet 26 is beneficial because it promotes arc interruption at current zero. On the other hand, in the region of the runners, e.g., point y, a phase lag of this amount is detrimental because arc interruption seldom is achieved in this region and the reverse force on the are following current zero drives the are back on the contacts.

We have also discovered that blow out magnets provided with spiral wound laminated pole shoes produce substantially less phase shift of the propelling flux in the region of the arc runner than in the region of the vertexes in the arc chute. This variation in phase angle lag is due mainly to the variation of the length of the flux path in iron for fiux crossing the air gap between pole pieces at progressively increasing distances along the longitudinal axis of the pole pieces. Flux crossing between the pole pieces in the region of the point x has a greater portion of its path in iron than does flux crossing the air gap in the region of the point y. Consequently phase angle lag, which is produced by eddy currents, is greater for the flux having the longer path in iron. The relationship between phase lag and distance from the arc runner for a pole shoe for a typical breaker is illustrated graphically in FIG. 8 by the curve 40 of which ordinates represent phase angle lag and abscissae represent distance from the arc runner measured along the longitudinal axis of a pole shoe. The lesser amount of phase shift of the fiux in the region of the arc runner substantially reduces the tendency to failure to interrupt resulting from driving arcs in the throat of the arc runners back toward the arcing contacts immediately following a current zero. The shape of the curve 40 can be changed to a considerable extent by variations in the construction and in the geometry of the core. For example a solid core increases the phase angle lag, owing to the increased amount of eddy currents. Removing the core entirely thereby to produce an air core very materially decreases the phase shift. Radial saw cuts in a spiral core produce an amount of phase shift intermediate the amounts produced by the solid core and the air core. Thus, combinations of these structural changes in varying ratios will result in substantial alteration in the shape of curve 40 as may be desired.

An additional advantage of the spirally laminated pole shoe is that the entire assembly of pole pieces and yoke illustrated in FIG. 4 can be automatically wound thereby eliminating the costly hand stacking of hundreds of separate laminations. In the stacked construction the laminations are stacked on insulated studs which requires holes in the laminations. The spirally wound pole shoes, on the other hand, require no machining of any kind.

The combination of the spiral wound pole shoes with an interconnecting yoke having a round cross section produces a flux distribution pattern in the spiral layers of the shoes that is illustrated in the upper righthand quadrant of FIG. 5 in which the arrows represent the flux generated by the arc current in the coil and yoke which has extended into the pole shoes. As shown the flux passes directly from the yoke through the butt joint and into each layer of the spiral wound shoe from the center to the outermost layer without having to cross an air gap between adjacent layers. Consequently the flux leaving the face of the pole shoe to cross the air gap in the arc chute to the opposite pole shoe is substantially evenly distributed across the face of the pole shoe from one longitudinal edge to the other as illustrated by the curve 41 which represents the distribution of flux at the section A-A. Ordinates of curve 41 represent flux and abscissae represent distance along the section line AA from left to right. With an even distribution or flux such as represented by curve 41, the arc tends to move evenly into the arc chute without any bonds or loops being formed in it as illustrated in FIG. 6.

If a round yoke of the same cross section as the yoke 34 were used in combination with a flat stacked lamination pole shoe such as illustrated in the lower righthand quadrant of FIG. 5 an uneven distribution of fiux across the face of the shoe would result. This uneven distribution results from the flux having to cross successive air gaps between the laminations in order to reach the outer laminations. Consequently the flux decreases toward the edges of the pole shoe as represented graphically by the curve 42 F! in the lower lefthand. quadrant of FIG. 1 which represents the flux distribution across the section BB of the stacked lamination yoke. Such an uneven distribution of flux across the faces of the pole shoes imparts to the are a sinusoidal wave shape with forward and reverse loops which have a tendency to force the are back on to the arc runners or even into the contact region to restrike the arc across the contacts and thus result in an interruption failure.

Since an even distribution of flux across the face of the pole shoe results when spirally Wound pole shoes are interconnected by a yoke having a round cross section,

round exciting coils may be mounted on the yokes. Thus,

the invention makes it possible to use the mechanically strong and etficient round coil instead of the not so strong and less eflicient rectangular coil.

Although a specific embodiment of the invention has been shown and described and the principle of the invention has been explained together with the best manner in which it is now contemplated applying the principle, it will be understood that the embodiment shown and described is merely illustrative and that the invention is not limited thereto since alterations and modifications will readily suggest themselves to persons skilled in the art without departing from the true spirit of the invention or from the scope of the annexed claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A circuit interrupter including means for establishing an arc and a magnet structure for extinguishing the arc comprising a pair of pole pieces arranged in parallel spaced apart relationship and each comprising insulated substantially continuous magnetic ribbon material formed into a spiral coil with each layer in physical contact with contiguous layers and an interconnecting yoke member generally perpendicular to the general planes of said shoes.

2. A circuit interrupter including means for establishing an arc and a magnetic structure for extinguishing the arc comprising a pair of pole shoes arranged in spaced apart relationship with their pole faces facing each other, each pole shoe comprising insulated substantially continuous magnetic ribbon material flat wound to form a tight spiral coil with each layer in contact with adjacent layers and the aligned edges of said layers on one side constituting the pole face, and an interconnecting yoke member generally perpendicular to the general planes of said shoes.

3. A circuit interrupter including means for establishing an arc, and a magnet structure for extinguishing the are including a pair of pole shoes each comprising a substantially continuous strip of magnetic material formed into a fiat spiral coil of generally oblong shape and an interconnecting yoke portion comprising a continuous strip of magnetic material formed into a spiral coil having an axis generally perpendicular to the planes of said shoes.

4. A circuit interrupter including means for establishing an arc, and a magnet structure for extinguishing the are including a pair of pole shoes, each pole shoe comprising a pair of pole pieces of generally oblong configuration arranged in spaced apart relationship with their pole faces facing each other, each pole shoe comprising an insulated substantially continuous ribbon of magnetic material flat wound to form a tight fiat spiral coil with each layer in contact with adjacent layers and the aligned edges on one side constituting the pole face, and an interconnecting yoke member comprising a substantially continuous ribbon of magnetic material formed into a spiral coil having an axis substantially perpendicular to the general planes of said shoes.

References Cited in the file of this patent UNITED STATES PATENTS 1,547,407 Breeze Iuly28, 1925 2,534,312 Somerville Dec. 19, 1950 2,632,075 Rawlins et al Mar. 17. 1953 

